<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<title>canvas</title>
</head>
<body>

<canvas id="myCanvas" width="300" height="150" style="border:1px solid #d3d3d3;">
	您的浏览器不支持 HTML5 canvas 标签。
</canvas>
<script>
    var c=document.getElementById("myCanvas");
    var ctx=c.getContext("2d");
    ctx.shadowBlur=10;
    ctx.shadowOffsetY=20;
    ctx.shadowColor="black";
    ctx.fillStyle="red";
    ctx.fillRect(20,20,100,80);
</script>

</body>
</html>